J/MNRAS/521/148 Stellar properties of Sun-like stars SDST III (Lehmann+, 2023)
Survey for Distant Solar Twins (SDST).
III. Identification of new solar twin and solar analogue stars.
Lehmann C., Murphy M.T., Liu F., Flynn C., Smith D., Berke D.A.
<Mon. Not. R. Astron. Soc. 521, 148-159 (2023)>
=2023MNRAS.521..148L 2023MNRAS.521..148L (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, normal ; Stars, G-type ; Spectroscopy ;
Optical ; Infrared ; Effective temperatures ; Abundances ;
Equivalent widths ; Radial velocities ; Photometry ;
Stars, distances ; Stars, ages ; Stars, activity ; Stars, masses ;
Magnitudes, absolute ; Stars, diameters
Keywords: instrumentation: spectrographs - methods: data analysis -
techniques: spectroscopic - stars: fundamental parameters -
stars: solar-type
Abstract:
The Survey for Distant Solar Twins aims to find stars very similar to
the Sun at distances of 1-4kpc, several times more distant than any
currently known solar twins and analogues. The goal is to identify the
best stars with which to test whether the fine-structure constant,
α, varies with dark matter density in our Galaxy. Here, we use
EPIC, our line-by-line differential technique, to measure the stellar
parameters - effective temperature Teff, surface gravity log g, and
metallicity [Fe/H] - from moderate-resolution (R ≲ 32000) spectra of
877 solar twin and analogue candidates (547 at 1-4kpc) observed with
the High Efficiency and Resolution Multi-Element Spectrograph (HERMES)
on the Anglo-Australian Telescope. These are consistent with
expectations for Teff and log g from photometry, and for [Fe/H] from
the Besancon stellar population model. EPIC provides small enough
uncertainties (∼90K, 0.08dex, and 0.05dex, respectively), even at the
low signal-to-noise ratios available (S/N ~> 25 per pixel), to
identify 299 new solar analogues (=> 90 per cent confidence) and
20 solar twins (=> 50 per cent confidence), 206 and 12 of which are at
1-4kpc. By extending EPIC to measure line broadening and lithium
abundance from HERMES spectra, and with ages derived from isochrone
fitting with our stellar parameters, we identify 174 solar analogues
at 1-4kpc that are relatively inactive, slowly rotating, and with no
evidence of spectroscopic binarity. These are the preferred targets
for follow-up spectroscopy to measure α.
Description:
The aim of the Survey for Distant Solar Twins (SDST) is to find and
spectroscopically confirm distant (up to 4kpc) solar twins and
analogues. This paper (the third in a series) presents the new solar
twin and analogue stars from our observations with HERMES at the 3.9m
AAT. The survey design, observations, data processing, and
verification of survey data products are presented in Liu et al.
(2022MNRAS.517.5569L 2022MNRAS.517.5569L, Cat. J/MNRAS/517/5569, Paper II). The epic
algorithm to determine stellar parameters differentially using a solar
reference spectrum is discussed in Lehmann et al.
(2022MNRAS.512...11L 2022MNRAS.512...11L, Paper I). This method is capable of determining
stellar parameters with low uncertainties for target stars using low
SNR HERMES spectra with medium resolving power (i.e see section
Introduction). We have observed 877 solar twin candidate stars in a
direction close to the Galactic Centre. We present two major results
in this work: the target stars with the highest probability to be
solar twin and analogue stars and the stars that are best suited for
observations of the fine-structure constant. The main difference
between these groups is that active stars, or stars with much broader
lines than the Sun (from e.g. rotation or spectroscopic binarity), are
not suited to be probes for α while they can still be solar twin
candidates. HERMES/AAT program is available at
https://archives.datacentral.org.au/query with program ID A/2021A/005.
Based on (Teff, logg, [Fe/H]) measured with EPIC, we computed stellar
activity indicators (A(Li), EW(Li), line br) as described in section
3. More as explicited in section 3.3, we determine stellar parameters
(Age, M*, logL, MV, R*) with qoyllur-quipu (q2) algorithm of Ramirez
et al. (2014A&A...572A..48R 2014A&A...572A..48R). Finally as fully detailled in section 4
analysis of results, we identify solar twins and analogues by using
stellar parameters and their associated uncertainties to calculate the
probability for each star to be a solar twin and analogue. We assume
Gaussian probability functions defined by equation 10,11,12 of this
section. The table.dat regroups stellar parameters results from EPIC,
q2, activity indicators and probabilities for all 877 selected
sources.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 764 877 EPIC spectroscopic measured parameters
(Teff, logg, [Fe/H]) and (EW, br, RV), and
computed stellar parameters with q2 algorithm
(Age, M*, logL, MV, R*)
--------------------------------------------------------------------------------
See also:
J/MNRAS/517/5569 : Stellar properties of Sun-like stars from SDST II
(Liu+, 2022)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
J/MNRAS/463/696 : M67 solar twins chemical compositions (Liu+, 2016)
J/MNRAS/325/1365 : Solar neighbourhood metallicity distribution (Haywood+,2001)
J/A+A/660/A135 : 62 Galactic open clusters abundances
(Viscasillas-Vazquez+, 2022)
J/A+A/640/A81 : Abundances of 72 solar-type stars (Nissen+, 2020)
J/A+A/639/A127 : Age-chemical-clocks-metallicity relations (Casali+, 2020)
J/A+A/562/A71 : Chemical abundances of solar neighbourhood dwarfs
(Bensby+, 2014)
J/A+A/545/A32 : Chemical abundances of 1111 FGK stars (Adibekyan+, 2012)
J/ApJ/808/16 : The Cannon: a new approach to determine abundances
(Ness+, 2015)
J/AJ/156/18 : APOGEE DR14:Binary companions of evolved stars
(Price-Whelan+, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaEDR3 The ID as can be found in Gaia's early
data release 3 (Gaia Collaboration et al.
2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350)
(GaiaeDR3ID)
21- 26 F6.1 K Teff The effective temperature measured by the
EPIC algorithm (teff)
28- 32 F5.1 K e_Teff The uncertainty of teff (err_teff)
34- 39 F6.4 [cm/s2] logg The surface gravity measured by the EPIC
algorithm (logg)
41- 46 F6.4 [cm/s2] e_logg The uncertainty of logg (err_logg)
48- 55 E8.5 [Sun] [Fe/H] The metallicity measured by the EPIC
algorithm (feh)
57- 63 F7.5 [Sun] e_[Fe/H] The uncertainty of feh (err_feh)
65- 68 F4.1 --- SNRB The signal-to-noise ratio in the B band
(SNR_B) (1)
70- 73 F4.1 --- SNRG The signal-to-noise ratio in the G band
(SNR_G) (1)
75- 78 F4.1 --- SNRR The signal-to-noise ratio in the R band
(SNR_R) (1)
80- 83 F4.1 --- SNRIR The signal-to-noise ratio in the IR band
(SNR_IR) (1)
85- 92 E8.5 [Sun] A(Li) The lithium abundance measured as
described in Lehmann et al.
(2022zndo...7332606C) (A_Li)
94-101 F8.5 [Sun] e_A(Li) The uncertainty of A (Li) (errALi)
103-110 F8.5 --- EW(Li)sig The sigma significance with which the
lithium line at 6707Å was detected
(LiEWsignificance)
112-118 F7.5 0.1nm br The broadening of the reference spectrum
measured as described in Lehmann et al.
(2022zndo...7332606C) (br_ref)
120-126 F7.5 0.1nm e_br The uncertainty of br (errbrref)
128-135 F8.5 0.1nm brt The broadening of the target spectrum
measured as described in Lehmann et al.
(2022zndo...7332606C) (br_tar)
137-143 F7.5 0.1nm e_brt The uncertainty of brtar (errbrtar)
145-154 F10.5 km/s RV The overall most likely radial velocity
measurement determined by the EPIC
algorithm (RV)
156-159 A4 --- f_RV A string flag for RV measurement (RV_flag)
(2)
161-181 F21.16 km/s RVB The radial velocity of the B band measured
by the EPIC algorithm (RV_B)
183-203 F21.16 km/s RVV The radial velocity of the V band measured
by the EPIC algorithm (RV_V)
205-225 F21.16 km/s RVR The radial velocity of the R band measured
by the EPIC algorithm (RV_R)
227-247 F21.16 km/s RVIR The radial velocity of the IR band
measured by the EPIC algorithm (RV_IR)
249-253 F5.2 mag Gmag The G magnitude as measured by Gaia (Gmag)
255-272 F18.15 mag Vmag The V magnitude as measured by Gaia (Vmag)
274-281 F8.6 mag e_Vmag The uncertainty of Vmag (err_Vmag)
283-291 F9.4 --- Plx The parallax as measured by Gaia (plx)
293-312 F20.18 --- e_Plx The uncertainty of plx (err_plx)
314-323 F10.5 pc rgeo [] The median distance derived from plx
(rmedgeo)
325-334 F10.5 pc b_rgeo [] The lower estimate of the distance
derived from plx (rlogeo)
336-347 F12.6 pc B_rgeo [] The upper estimate of the distance
derived from plx (rhigeo)
349-358 F10.5 pc rpgeo [] The median distance derived from plx
and the photometric magnitudes
(rmedphotogeo)
360-381 F22.17 pc b_rpgeo [] The lower estimate of the distance
derived from plx and the photometric
magnitudes (rlophotogeo)
383-394 F12.6 pc B_rpgeo [] The upper estimate of the distance
derived from plx and the photometric
magnitudes (rhiphotogeo)
396-402 F7.1 mJy Flux The median measured flux with HERMES
(MedianFlux)
404-409 F6.2 mJy e_Flux The median sigma uncertainty for
measurements with HERMES (MedianSigma)
411-416 F6.1 K Teffnc The effective temperature measured by the
EPIC algorithm using the initial non
corrected photometric calibration (teff_nc)
418-423 F6.1 K e_Teffnc The uncertainty of teff_nc (errteffnc)
425-430 F6.4 [cm/s2] loggnc The surface gravity measured by the EPIC
algorithm using the initial non corrected
photometric calibration (logg_nc)
432-439 F8.4 [cm/s2] e_loggnc The uncertainty of logg_nc (errloggnc)
441-448 E8.5 [Sun] [Fe/H]nc The metallicity measured by the EPIC
algorithm using the initial non corrected
photometric calibration (feh_nc)
450-456 F7.5 [Sun] e_[Fe/H]nc The uncertainty of feh_nc (errfehnc)
458-461 F4.1 Gyr Agemp ? Age q2 output code (age_mp) (3)
463-468 F6.3 Gyr e_Agemp ? Age lower limit (1sigma) q2 output code
(age_ll1s)
470-475 F6.3 Gyr E_Agemp ? Age upper limit (1sigma) q2 output code
(age_ul1s)
477-482 F6.3 Gyr e2_Agemp ? Age lower limit (2sigma) q2 output code
(age_ll2s)
484-489 F6.3 Gyr E2_Agemp ? Age upper limit (2sigma) q2 output code
(age_ul2s)
491-496 F6.3 Gyr Agemean ? Mean age q2 output code (age_mean) (3)
498-502 F5.3 Gyr e_Agemean ? Standard deviation of mean age Agemean
q2 output code (age_std)
504-507 F4.2 Msun M*mp ? Mass q2 output code (mass_mp) (3)
509-513 F5.3 Msun e_M*mp ? Mass lower limit (1sigma) q2 output code
(mass_ll1s)
515-519 F5.3 Msun E_M*mp ? Mass upper limit (1sigma) q2 output code
(mass_ul1s)
521-525 F5.3 Msun e2_M*mp ? Mass lower limit (2sigma) q2 output code
(mass_ll2s)
527-531 F5.3 Msun E2_M*mp ? Mass upper limit (2sigma) q2 output code
(mass_ul2s)
533-537 F5.3 Msun M*mean ? Mean mass q2 output code (mass_mean) (3)
539-543 F5.3 Msun e_M*mean ? Standard deviation of mean age Agemean
q2 output code (mass_std)
545-549 F5.2 [Lsun] logLmp []? Logarithm of stellar luminosity q2
output code (logl_mp) (3)
551-556 F6.3 [Lsun] e_logLmp []? Logarithm of stellar luminosity lower
limit (1sigma) q2 output code (logl_ll1s)
558-563 F6.3 [Lsun] E_logLmp []? Logarithm of stellar luminosity upper
limit (1sigma) q2 output code (logl_ul1s)
565-570 F6.3 [Lsun] e2_logLmp ? Logarithm of stellar luminosity lower
limit (2sigma) q2 output code (logl_ll2s)
572-577 F6.3 [Lsun] E2_logLmp ? Logarithm of stellar luminosity upper
limit (2sigma) q2 output code (logl_ul2s)
579-584 F6.3 [Lsun] logLmean ? Logarithm of mean stellar luminosity q2
output code (logl_mean) (3)
586-590 F5.3 [Lsun] e_logLmean ? Logarithm of standard deviation of mean
stellar luminosity logLmean q2 output code
(logl_std)
592-595 F4.2 mag vmpMag ? Absolute V magnitude q2 output code
(mv_mp) (3)
597-601 F5.3 mag e_vmpMag ? Absolute V magnitude lower limit
(1sigma) q2 output code (mv_ll1s)
603-607 F5.3 mag E_vmpMag ? Absolute V magnitude upper limit
(1sigma) q2 output code (mv_ul1s)
609-613 F5.3 mag e2_vmpMag ? Absolute V magnitude lower limit
(2sigma) q2 output code (mv_ll2s)
615-619 F5.3 mag E2_vmpMag ? Absolute V magnitude upper limit
(2sigma) q2 output code (mv_ul2s
621-625 F5.3 mag vmeanMag ? Mean absolute V visual magnitude q2
output code (mv_mean) (3)
627-631 F5.3 mag e_vmeanMag ? Standard deviation of mean vmeanMag q2
output code (mv_std)
633-636 F4.2 Rsun R*mp ? Stellar radius q2 output code (r_mp) (3)
638-642 F5.3 Rsun e_R*mp ? Stellar radius lower limit (1sigma) q2
output code (r_ll1s)
644-648 F5.3 Rsun E_R*mp ? Stellar radius upper limit (1sigma) q2
output code (r_ul1s)
650-654 F5.3 Rsun e2_R*mp ? Stellar radius lower limit (2sigma) q2
output code (r_ll2s)
656-660 F5.3 Rsun E2_R*mp ? Stellar radius upper limit (2sigma) q2
output code (r_ul2s)
662-666 F5.3 Rsun R*mean ? Mean stellar radius magnitude q2 output
code (r_mean) (3)
668-672 F5.3 Rsun e_R*mean ? Standard deviation of mean stellar
radius R*mean q2 output code (r_std)
674-695 E22.19 --- PST The likelihood of a star to be a solar
twin (P_ST) (4)
697-718 E22.19 --- PSA The likelihood of a star to be a solar
analogue (P_SA) (4)
720-741 E22.19 --- PSTnc The likelihood of a star to be a solar
twin and using the initial non corrected
photometric calibration (PSTnc) (4)
743-764 E22.19 --- PSAnc The likelihood of a star to be a solar
analogue and using the initial non
corrected photometric calibration
(PSAnc) (4)
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Note (1): Measured as described in Liu et al. (2022MNRAS.517.5569L 2022MNRAS.517.5569L,
Cat. J/MNRAS/517/5569) and Lehmann et al. (2022zndo...7332606C).
Note (2): Made of either "F" or "T". "FFFF" indicates that all bands have
measured the same radial velocity while a T in any position indicates
that one of the bands has measured an unlikely radial velocity
(e.g. "FTFF" indicates that the the G band radial velocity differs
from the others)
Note (3): Measured values of the q2 algorithm to calculate elemental abundances
of stars and/or determine their atmospheric parameters using the
standard techniques of iron line excitation/ionization equilibrium.
It also allows you to calculate other fundamental stellar parameters
such as mass and age using isochrones available at website,
(https://github.com/astroChasqui/q2).
Note (4): According to the solar twin definition in Berke et al.
(2023MNRAS.519.1238B 2023MNRAS.519.1238B) and stellar parameters calculated by EPIC
(using the initial non corrected photometric calibration when "nc"
is written).
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History:
From electronic version of the journal
References:
Lehmann et al., Paper I 2022MNRAS.512...11L 2022MNRAS.512...11L
Liu et al, Paper II 2022MNRAS.517.5569L 2022MNRAS.517.5569L, Cat. J/MNRAS/517/5569
Lehmann et al., Paper III This work
License: CC-BY-4.0
(End) Luc Trabelsi [CDS] 19-May-2026